Drafting machine braking system

ABSTRACT

Operating levers for controlling the horizontal and vertical movement of a track-type drafting machine are mounted on the vertical motion carriage and are at all times within the functional span of the hand of a draftsman grasping the protractor drafting head. Actuation of the brake assembly carried by the horizontal motion carriage is effected by means of a cord loop extending between the carriages with movement of the operating lever drawing the cord through a dead center point of maximum tension, thus providing for the retention of the brake in the desired released or engaged condition.

United States Patent [1 1 I Kooi [451 Sept. 30, 1975 1 1 DRAFTINGMACHINE BRAKING SYSTEM [75] Inventor: .1. Peter E. Kooi, Succasunna. NJ.

[73] Assignee: Keuffel & Esser Company,

Morristown, NJ.

[22] Filed: Feb. 25, 1974 Appl. No.: 445,709

US. Cl. 33/76 R; 33/79 R B43L 13/02 Field of Search 33/79. 76 R [56]References Cited UNITED STATES PATENTS 2.102.636 12/1937 McDonald 33/79R 3.279.073 10/1966 Ardito et al. 33/79 R 3,400,461 9/1968 Faul 33/79 R3.761055 10/1973 Citrin .7 33/81 3.823.479 7/1974 Komabayashi et a133/76 R Priniary E.\'uminerRichard E. Aegerter .4ssisranlE.\'aminer.lohn W. Shepperd Attorne v.'Agen/ or FirmLionel N. White,Esq.

ABSTRACT Operating levers for controlling the horizontal and verticalmovement of a track-type drafting machine are mounted on the verticalmotion carriage and are at all times within the functional span of thehand of a draftsman grasping the protractor drafting head. Actuation ofthe brake assembly carried by the horizontal motion carriage is effectedby means of a cord loop extending between the carriages with movement ofthe operating lever drawing the cord through a dead center point ofmaximum tension, thus providing for the retention of the brake in thedesired released or engaged condition.

2 Claims, 3 Drawing Figures U.S. Patent Sept. 30,1975 Sheet 1 of 23,908,276

US. Patent Sept. 30,1975 Sheet 2 of2 3,908,276

FIG. 3

BACKGROUND In recent years. track-type drafting machines have foundincreasing acceptance in the engineering drawing field. Such devicesgenerally comprise a stationary horizontal track affixed to the top edgeof a drafting board or table and along which a wheeled carriage isguided to provide a freedom of movement across the board in thehorizontal direction.

Attached to and moving with the horizontal track carriage is a verticaltrack member along which is guided a second wheeled carriage to providevertical motion over the drafting surface. The usual protractor draftinghead is attached to the vertical track carriage and as a result of theorthoganal movements provided by the carriages is enabled to move to anypoint on the drafting surface.

During the course of the preparation of an engineering drawing, however,it is generally required that the two degrees of freedom of movement ofthe drafting head be individually or jointly arrested to enable thedraftsman to complete various drafting operations. Such arresting ofmovement has for the most part simply been accomplished by individualbraking members carried by each of the carriages and which may beactuated to engage the respective track members, thereby immobilizingthe head with respect to the relevant direction of movement.

Of particular concern to the draftsman is the capability of actuatingthe respective braking members with the least interruption to hisdrafting procedure, and thus it is most desirable that brake-actuatingcontrols be available to the hand of the draftsman which engages theprotractor head during normal drafting operations.

Little problem exists in providing such an arrangement for actuating thevertical motion braking means, since the protractor head is physicallyassociated with and moves in the same direction as the vertical motioncarriage. The vertical brake control is, as a result, at all timeswithin the ready grasp of the draftsmans hand. Actuation of the brake onthe horizontal motion carriage, on the other hand, has continuouslypresented a problem due to the varying distance between the horizontalmotion carriage and the protractor head during vertical movement of thehead.

Designers of earlier track-type drafting machines have attempted innumerous ways to satisfy the noted requirement of convenience in theactuation ofthe horizontal carriage brake.

The ultimate convenience of an electrical system for operating thebrakes of a drafting machine, as described in U.S. Pat. No. 3,153,284 isquite apparent; however, the added cost, complexity, and power requirement limitations of such an arrangement were found to outweigh theadvantage of convenience.

The greater simplicity and lower expense of mechanical means thusprompted the designers of the machines described in U.S. Pat. No.3,074,173; U.S. Pat. No. 3,279,073; and U.S. Pat. No. 3,400,461 toemploy an elongated horizontal brake actuation control member extendinggenerally over the length of the vertical track to provide manualaccessibility to the draftsman of that control member regardless of thedistance of the protractor head from the horizontal track. Althoughthese devices provided some satisfaction of the demand for convenience,the fact that the brake control member, while accessible, was notcapable of moving with the vertical motion carriage caused draftsmen tofind that in actual practice horizontal brake actuation requiredmovement of the protractor operating hand from that station.

A brake-actuating system described in U.S. Pat. No. 2,102,636 embodiedthe desirable feature wherein movement of a horizontal brake controlmember was, in fact, associated with the movement of the vertical motioncarriage. That system, however, did not entirely satisfy the demands ofthe draftsman, since the critical actuating elements were so arranged asto require the removal of the draftsmans hand from the arena of theprotractor head, thus rendering horizontal motion braking duringdrafting activity a two-handed operation.

The present invention provides an improvement in the device generallydescribed in U.S. Pat. No. 2,102,636 whereby either or both of thehorizontal and vertical track carriage brake may be actuated by thedraftsman from any location on a drafting board without a need for hismoving the operating hand from the protractor head of the draftingmachine.

SUMMARY In accordance with the present invention, a drafting machinebraking system is provided which includes a running cord loop anchoredto the vertical carriage and encompassing brake actuating means situatedat the horizontal motion carriage and manually accessible control meanssituated at the vertical motion carriage. As a result of the cord loopfeature, the control means is constantly in communication with thehorizontal motion braking assembly regardless of the distance betweenthe horizontal and vertical carriages.

The horizontal brake control means carried by the vertical carriagecomprises a pivoted lever to the proximal arm of which is attached theterminal end of the cord forming the control loop. A control member atthe end of the distal lever arm is movable through a short are withinthe span of the draftsmans hand from the protractor head and by suchmovement causes the lever to apply tension to the control cord during aportion of the arcuate sweep of the lever arm. Such tension results in ashortening of the loop and thus transfers the draftsmans effort to thebrake assembly of the horizontal carriage.

The proximal arm of the brake control lever is so disposed, however,with respect to the attitude of the terminal reach of the cord to whichit is attached that completion of the arcuate sweep of the lever carriesthe arm through a dead center point of maximum cord tension and into aposition which is thereafter maintained by the reactive tension of thecord upon the lever arm. By virtue of the arrangement of the controllever assembly, the noted dead center point is located at a distancefrom the center of the arcuate sweep of the lever and thereby results ina difference between the cord tensions at the arc termini. Such cordtension difference establishes the respective engaged and releasedconditions of the horizontal brake.

A similar control lever actuating arrangement is provided with respectto the vertical motion brake; however, since both the actuating andbraking means are located at the vertical carriage, the need for acontrol cord is eliminated and the lever action is applied directly. Thecontrol member for this second braking assembly is situated closelyadjacent that of the horizontal brake control lever, thereby placing allbraking controls and the protractor head within a single span of thedraftsmans hand.

DRAWINGS In the accompanying drawings:

FIG. 1 depicts a track-type drafting machine mounted upon a drawingboard and reveals, in partial cut-away, carriage assemblies embodying abraking system according to the present invention;

FIG. 2 shows in greater detail a drafting machine horizontal motioncarriage with braking means according to the present invention; and

FIG. 3 shows in greater detail a drafting machine vertical motioncarriage with braking means according to the present invention.

DESCRIPTION The present improvement in track-type drafting machinebraking means may be particularly described by reference to theaccompanying drawings which depict a simple embodiment of the inventionwhereby a cord loop trained about a horizontal motion arrestingmechanism and attached to a control member mounted upon the verticalmotion carriage provides positive and selfsustained braking actuablefrom any location of the drafting machine head on a drafting boardsurface.

In FIG. 1 there is mounted along the upper edge of drafting board bymeans of mounting brackets 12 (one of which is shown) the horizontaltrack member 20'of a track-type drafting machine. In a manner well knownfrom previous similar drafting machines as above-noted, a wheeledhorizontal motion carriage 22 is arranged to move along parallel tracksassociated with track member 20 to thereby provide the horizontal degreeof motion freedom to the drafting machine.

Mounted on carriage 22 is a braking assembly, shown generally at 24 andto be described later in more detail, comprising a pivotted lever armmounting a brake shoe with spring means biasing the lever arm tomovement in a direction to engagethe brake shoe with a surface of trackmember 20.

Additionally affixed to horizontal carriage 22 by well-known means notshown is a vertically disposed track member 30. Mounted at the lower endof vertical member 30 is wheel assembly 18 which provides track member30 with support for its movement with carriage 22 across the width ofdrawing board 10.

Arranged for movement along vertical member 30 in the manner previouslydescribed with respect to the horizontal carriage is a generally similarvertical carriage 32 to which is pivotally mounted through a yoke 16 theprotractor drafting head assembly 14 of the drafting machine.

A braking assembly 34 similar to assembly 24 of carriage 22 is pivotallymounted on vertical motion carriage 32 and provides the means forarresting motion of carriage 32 and drafting head 14 in the verticaldirection. Brake actuating controls 15, 17 located at the respectivedistal ends of lever arms 37, 36 pivotally mounted on vertical carriage32 are positioned within the span of a draftsmans hand stationed atdrafting head 14. Means for actuating vertical motion brake assembly 34to govern movement of carriage 32 may be seen to generally compriselever 36 which, upon movement of control member 17, effects withdrawalof the vertical brake shoe from engagement with track member 30. Furtherdetail in the operation of this brake actuating means will be given withreference to FIG. 3.

Actuating means for horizontal brake assembly 24 to control movement ofcarriage 22 along track member 20 is simply and schematicallyrepresented in the drawings by a lever 26 pivotally mounted tohorizontal carriage 22 and communicating between vertical brake leverarm 24 and pulley member 27. Such a schematic representation should notdetract from a complete understanding of the present invention; however,since it will be readily understood by those familiar with tracktypedrafting machines, such as are described in the aforementioned patentspecifications, that the additional elements of the present embodimentof the invention may be employed as well to actuate complex lever trainbrake mechanisms housed in bridging assemblies often used to mount thevertical track member upon the horizontal carriage. Thus, by consideringthe response and effect of brake actuating lever 26 in the actionsdescribed below, one will derive no less a complete description of theinstant invention.

Means for transferring brake-actuating effort from the draftsmansfingertip to braking assembly 24 comprises a cord or cable 13 which isanchored at one end to vertical carriage 32, trained about actuatinglever pulley 27 and a stationary pulley 19 mounted on vertical trackmember 30 near its lower end, and affixed at its terminal end to leverarm 37, thereby forming of the cord a running loop extendingsubstantially the entire length of track member 30. Thus it will be seenthat the loop of cord will trail the vertical movement of carriage 32and that tension applied to the cable at its mobile end by movement oflever arm 37 will effect a shortening of the cord loop and cause adownward movement of pulley 27 with resulting actuation of brakeassembly 24 to disengage the horizontal carriage brake from track member20. In drafting machines which employ a counterweight (not'shown here)for the vertical carriage/drafting head assembly, cord 13 may serve adual function as both brake control loop and counterweight cord.

In FIG. 2 is shown the enlarged and more detailed view of horizontalmotion carriage 22 and the horizontal motion braking assembly mountedthereon. On body plate 22 of the carriage are mounted wheels 23 whichare in rolling engagement with parallel track surfaces 21 of horizontaltrack member 20.

Mounted on body plate 22 at pivot stud 25 is horizontal brake lever arm24 with affixed brake shoe bracket 42 carrying brake shoe 43. To arm 24is attached one of a pair of spring brackets 45, 45, the other of whichis affixed to body plate 22. Extending between these spring brackets iscompression spring 44 which biases lever arm 24 in a counter-clockwisedirection about pivot 25 toward position 24' at which brake shoe 43'engages track inner edge surface 29 to arrest movement of the horizontalcarriage along track member 20.

Mounted on carriage body plate 22 at a pivot stud 28 is horizontal brakeactuating lever 26, the distal end of which pivotally supports a pulley27. At the proximal end of lever 26 is disposed a slot 47 which receivesa stud 46 mounted at the distal end of brake lever arm 24. Trained aboutpulley 27 is the upper reach of the loop of cord, leg 13 being anchoredat its end to vertical motion carriage 32 with leg 13"being the tensionleg as will be seen in later discussion. It will thus be apparent thatdownward tension at cord leg 13 will displace actuating lever pulley toposition 27 where lever movement through stud and receiver slot junction46, 47, overcoming the bias of spring 44, moves the lever arm clockwiseabout pivot 25 to position 24 thereby lifting brake shoe 43 from tracksurface 29 to free the horizontal carriage for movement along trackmember As shown in FIG; 3, the vertical motion carriage comprises asimilar arrangement of carriage body plate 32 mounting wheels 33which'engage parallel track surfaces 31 of vertical track member 30.Braking of the vertical movement of carriage 32 along the vertical trackmember is effected in a manner similar to that earlier described withrespect to the horizontal motion carriage. To this end, body plate 32carries a braking assembly comprising brake lever arm 34 with brake shoebracket 52 and brake shoe 53 pivotted at stud 35 for counter-clockwisemovement under the biasing force of compression spring assembly 54, 55to engage brake shoe 53 with track member edge surface 39 to arrestmovement of the vertical carriage.

Release of the braking action of the vertical carriage brake assembly iseffected by downward movement of control member 17 and its associatedactuating lever 36 which is pivotally mounted upon body plate 32 at thestud 38. Such movement rotates lever arm 34 in a clockwise directionagainst the bias of spring 54 to lift brake shoe 53 from engagement withtrack member surface 39. In the interest of drawing clarity, the brakereleased position of the braking assembly and actuating lever 36 havenot been shown; however, it will be noted that a complete depression ofcontrol member 17 will cause the proximal arm of lever 36 to passthrough a dead center point of maximum displacement of lever arm 34,thence to the terminal position in its arcuate movement, where it isretained by the biasing force of spring 54. This selfmaintainingprovision of the present braking arrangements will be discussed later ingreater detail with respect to the action of the horizontal brakeactuating controls.

Mounted on pivot stud 38 at the underside of body plate 32 is horizontalbrake actuating lever 37 at the end of the proximal lever arm of whichis located stud 56. Movement of actuating lever 37 is effected byfingertip effort of the draftsman applied to control member affixed tothe end of the distal arm of lever 37. Located in body plate 32 isarcuate slot 57 through which lever arm stud 56 gains access to theupper side of body plate 32. The termini of slot 57 provide positivestops for stud 56 to limit the arcuate sweep of control member 15. Stopsengaging lever 37 may be likewise employed.

The horizontal brake control loop is formed when cord 13, anchored atstud 5] on vertical carriage body plate 32, is trained upward and abouthorizontal brake actuating lever pulley 27, thence downward and aboutstationary vertical track member pulley l9, thence about guide 62, andfinally to attachment to brake control lever arm stud 56.

It will be seen that slot 57 is so situated with respect to brakecontrol lever arm 37 and pivot stud 38 that slot termini stud positions56, 56 are at different distances from a common cord tangent point 63 onguide 62. Thus, movement of control member 15 between its terminalpositions 15, 15' effects a condition of greater or lesser tension uponcord 13, the greater at 15 overcoming the biasing force of horizontalbrake spring 44 with the resulting shortening of the cord loop todisplace pulley 27 and disengage the horizontal brake as earlierdescribed.

During'movement from the brake-engaged position, as located by systemelements 13', 15, 37', 56', to the brake-released position actuallydepicted, the proximal arm of lever 37 passes through a position atwhich the distance between stud 56 and the common tangent point 63 isthe greatest and, thus, at which cord extension and tension are amaximum. In the embodiment here described, such a dead center point ofmaximum cord tension occurs when the terminal cable leg 13" overlies thecenter of lever arm pivot 38 and is thus coicident coincident theproximal arm of control lever 37. Further movement beyond this deadcenter point of maximum tension to the brake-released terminus of slot57 allows the bias of spring 44, through its reactive tension upon cord13, to retain lever 37 in that terminal position and effect theself-maintaining feature of the braking system of the present invention.In order to ensure the efficacy of brake actuation the dead center pointmust, of course, be displaced from a mid-arc location. A point set ashort distance from one are terminus is preferred.

To damp the motion of control member 15 subsequent to its passing thedead center point toward the brake-engaged positon, it is desirable tointerpose a damping torsion spring 58 between stud 56 and an anchor stud59 on body plate 32. The torque of damping spring 58 is insufficient tocause any substantial decrease in the biasing force of horizontal brakeactuating spring 44.

What is claimed is:

1. In a drafting machine comprising a horizontally disposed trackmember, a horizontal motion carriage arranged to travel along thehorizontal track, a vertically disposed track member carried by saidhorizontal carriage for movement therewith, a vertical motion carriagearranged to travel along the vertical track, a drafting head carried bysaid vertical carriage for movement therewith and with said verticalmember, said drafting head thereby having two orthogonal degrees offreedom of movement over the surface of a drafting board, braking meansfor individually arresting the travel of each of said carriages tothereby limit the respective degrees of freedom of said drafting head,and means within reach of the hand of a draftsman grasping said draftinghead for actuating vertical motion carriage braking means, theimprovement in said braking means whereby actuation thereof to controlthe travel of both said carriages may at all times be effected by thehand of a draftsman stationed at said drafting head, said improvementcomprising:

a. a braking member including a brake shoe mounted on said horizontalmotion carriage for movement to and from carriage-arresting contact withsaid horizontal track member;

b. means carried by said horizontal motion carriage arranged to normallyurge said brake shoe into said carriage-arresting contact with saidhorizontal track member;

c. lever means coupled to said braking member arranged to transfer tosaid braking member actuating force applied to a distal arm thereof tothereby overcome said urging means and effect separation of saidcarriage-arresting contact between said brake shoe and horizontal trackmember;

' d. a pair of pulleys, the first being mounted on said lever meansdistal arm for movement therewith and the second being mounted fixedlyon said vertical track member, said pair of pulleys definingtherebetween the path of travel of said vertical motion carriage; v r

. a cord attached to said vertical motion carriage displacement of saidproximal lever arm effects a shortening of said loop through a minimumloop length, thereby displacing said lever arm-mounted pulley through amaximum with concurrent maximum displacement of said braking member andseparation between said brake shoe and horizontal track member; and

g. stop means limiting the displacement ofsaid control lever meansbeyond the position of said minimum loop length to a distance which isless than the displacement distance from the position of brake shoeengagement with said horizontal track member to said position of minimumloop length.

2. The invention according to claim 11 wherein said vertical motioncarriage braking means comprises:

a. a braking member including a brake shoe mounted on said verticalmotion carriage for movement to and from carriage-arresting contact withsaid vertical track member; 7

b. means carried by said vertical motion carriage arranged to normallyurge said brake shoe into said carriage-arresting contact with saidvertical track member; and

.a second control lever means pivotally mounted on said vertical motioncarriage with a distal lever arm thereof within the reach of the hand ofa draftsman grasping said drafting head and arranged to transfer to saidbraking member actuating force applied to said distal arm thereof ,tothereby overcome said .urging means and effect separation of saidcarriage-arresting contact between said brake shoe and vertical trackmember.

1. In a drafting machine comprising a horizontally disposed trackmember, a horizontal motion carriage arranged to travel along thehorizontal track, a vertically disposed track member carried by saidhorizontal carriage for movement therewith, a vertical motion carriagearranged To travel along the vertical track, a drafting head carried bysaid vertical carriage for movement therewith and with said verticalmember, said drafting head thereby having two orthogonal degrees offreedom of movement over the surface of a drafting board, braking meansfor individually arresting the travel of each of said carriages tothereby limit the respective degrees of freedom of said drafting head,and means within reach of the hand of a draftsman grasping said draftinghead for actuating vertical motion carriage braking means, theimprovement in said braking means whereby actuation thereof to controlthe travel of both said carriages may at all times be effected by thehand of a draftsman stationed at said drafting head, said improvementcomprising: a. a braking member including a brake shoe mounted on saidhorizontal motion carriage for movement to and from carriagearrestingcontact with said horizontal track member; b. means carried by saidhorizontal motion carriage arranged to normally urge said brake shoeinto said carriage-arresting contact with said horizontal track member;c. lever means coupled to said braking member arranged to transfer tosaid braking member actuating force applied to a distal arm thereof tothereby overcome said urging means and effect separation of saidcarriage-arresting contact between said brake shoe and horizontal trackmember; d. a pair of pulleys, the first being mounted on said levermeans distal arm for movement therewith and the second being mountedfixedly on said vertical track member, said pair of pulleys definingtherebetween the path of travel of said vertical motion carriage; e. acord attached to said vertical motion carriage and trained about saidpair of pulleys, thereby forming a loop including said vertical motioncarriage; f. control lever means pivotally mounted on said verticalmotion carriage with a distal lever arm thereof within the reach of thehand of a draftsman grasping said drafting head and with a proximallever arm thereof engaging said cord, whereby applied force displacingsaid distal lever arm with following displacement of said proximal leverarm effects a shortening of said loop through a minimum loop length,thereby displacing said lever arm-mounted pulley through a maximum withconcurrent maximum displacement of said braking member and separationbetween said brake shoe and horizontal track member; and g. stop meanslimiting the displacement of said control lever means beyond theposition of said minimum loop length to a distance which is less thanthe displacement distance from the position of brake shoe engagementwith said horizontal track member to said position of minimum looplength.
 2. The invention according to claim 11 wherein said verticalmotion carriage braking means comprises: a. a braking member including abrake shoe mounted on said vertical motion carriage for movement to andfrom carriage-arresting contact with said vertical track member; b.means carried by said vertical motion carriage arranged to normally urgesaid brake shoe into said carriage-arresting contact with said verticaltrack member; and c. a second control lever means pivotally mounted onsaid vertical motion carriage with a distal lever arm thereof within thereach of the hand of a draftsman grasping said drafting head andarranged to transfer to said braking member actuating force applied tosaid distal arm thereof to thereby overcome said urging means and effectseparation of said carriage-arresting contact between said brake shoeand vertical track member.